Varicella-Zoster virus (VZV) causes chickenpox and shingles. The goals of this project are to construct VZV mutants to identify VZV genes that are important in virus growth and latency, and to test whether these mutants could serve as candidate live virus vaccines by inoculating animals with the mutants. Inactivation of the VZV OR61 gene resulted in a virus that was impaired for growth in tissue culture cells, but its growth could be complemented in certain cell lines. Inactivation of this gene reduced the ability of the virus to form fused cells (syncytia) in vitro and impaired expression of late, but not immediate-early, viral proteins. A reporter gene (beta-galactosidase) was inserted into the VZV genome and guinea pigs were inoculated intraocularly with VZV expressing the reporter gene. The animals developed an eye infection (uveitis) with inflammatory cells in the eye that persisted for at least three months. Beta-galactosidase was expressed in various parts of the eye, including the retina and ciliary body for several months after infection.